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Trevor Jones
 
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Default How do I figure out the pressure angle on a gear - was usingmini-lathe for dividing head

jt wrote:

a poster in the previous thread replied as follows:
=======================
I don't need a lot of teeth hitting the worm-wheel, it's not like power
transmission is going on. How about a single worm with thread profile to
match the headstock gear? I'd have to tilt the worm at some small angle.
Maybe there's a source of threaded rod that would fit nicely...


Instead of a worm, how about a short rack? Spring pressure engages it
with the headstock gear, which can be advanced by a combination of (a)
whole tooth positions and (b) micrometer advance of the rack. The rack
is cut straight so there's no need for a small tilt angle.
========================

This would work for me. I wouuld be happy with the fine-ness of divisions
available with this, and small parts has rack - in two pressure angles.
Having looked this up I know what it is, but do not think I can measure the
teeth accurately enough to determine which I have. Is there another way?


Once you have the information calculating the info about your gear
from measurments, as mentioned in other posts, calculate the dimensions
for the rack tooth cutter for both the 20 deg. PA and 14.5 deg. PA.
Effectivly these will look like an acme threadding tool for the lathe
except on will have a 20 deg. included angle, the other, 14.5 deg. You
can then either use these measurements directly (measure the spaces
between teeth) or make a template that you can apply to the teeth of
your gear to see how it engages. If the 14.5 PA template bottoms in the
gap and the 20 deg PA one does not, it would be 20 deg PA. Conversly, if
the 20 deg. PA one sits too high in the gap, and the 14.5 deg one does
not bottom it would be 14.5 deg.

A couple calculations, a bit of plastic sheet stock and a razor knife,
and yer in there!

Cheers
Trevor Jones
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Trevor Jones
 
Posts: n/a
Default How do I figure out the pressure angle on a gear - was usingmini-lathe for dividing head

Trevor Jones wrote:

jt wrote:

a poster in the previous thread replied as follows:
=======================
I don't need a lot of teeth hitting the worm-wheel, it's not like power
transmission is going on. How about a single worm with thread profile to
match the headstock gear? I'd have to tilt the worm at some small angle.
Maybe there's a source of threaded rod that would fit nicely...


Instead of a worm, how about a short rack? Spring pressure engages it
with the headstock gear, which can be advanced by a combination of (a)
whole tooth positions and (b) micrometer advance of the rack. The rack
is cut straight so there's no need for a small tilt angle.
========================

This would work for me. I wouuld be happy with the fine-ness of divisions
available with this, and small parts has rack - in two pressure angles.
Having looked this up I know what it is, but do not think I can measure the
teeth accurately enough to determine which I have. Is there another way?


Once you have the information calculating the info about your gear
from measurments, as mentioned in other posts, calculate the dimensions
for the rack tooth cutter for both the 20 deg. PA and 14.5 deg. PA.
Effectivly these will look like an acme threadding tool for the lathe
except on will have a 20 deg. included angle, the other, 14.5 deg. You
can then either use these measurements directly (measure the spaces
between teeth) or make a template that you can apply to the teeth of
your gear to see how it engages. If the 14.5 PA template bottoms in the
gap and the 20 deg PA one does not, it would be 20 deg PA. Conversly, if
the 20 deg. PA one sits too high in the gap, and the 14.5 deg one does
not bottom it would be 14.5 deg.

A couple calculations, a bit of plastic sheet stock and a razor knife,
and yer in there!

Cheers
Trevor Jones


Doh! 40 deg. and 29 deg. included angles.

But if you have the info to calculate the angles, you probably worked
that out.

Cheers
Trevor Jones
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